uForth has been superceded by ToolForth ([https://github.com/tcoram/toolboxforth])
uForth is a highly portable ANSI Forth-like language. It can be easily ported to microcontrollers of all sizes. No dynamic memory allocation required.
It implements a "switch" threaded Forth. Not super fast, but portable!